Waveguide dissipating section using glass-iron composition absorber and method of making same



Feb. 8, 1966 J. E. EBERT 3,234,487

WAVEGUIDE DISSIPATINC SECTION USING GLASS-IRON COMPOSITION ABSORBER AND METHOD OF MAKING SAME Filed Aug. 16. 1961 Joy 5 f 66197 United States Patent WAVEGUIDE DISSIPATING SECTION USING GLASS-IRON COMPOSITION ABSORBER AND METHOD OF MAKING SAME John E. Ebert, Manhasset, N.Y., assignor to Ampheuol Corporation, a corporation of Delaware Filed Aug. 16, 1961, Ser. No. 131,786 4 Claims. (Cl. 333-22) The present invention relates to a waveguide dissipating section for microwave radio energy for use either as a waveguide attenuator or as a dummy load and relates more particularly to a dissipating section having an im proved power absorbing material.

Waveguide attenuators are in common use which have lossy materials provided in their inner walls for dissipat ing microwave radio energy. These lossy materials are formed of mixtures of iron powder and some type of binder. It has been found, however, that these known types of lossy materials experience rapid deterioration when subjected to high temperatures or to temperature cycling so that the amount of attenuation provided varies. These materials have also tended to separate from the waveguide walls and explosive steam pressures have also resulted in the waveguides from the heating of moisture absorbed by the materials.

The absorbing material of the present invention is me chanically and electrically stable through wide tempera ture fluctuations and also does not absorb moisture.

Accordingly, an object of the present invention is to provide an improved waveguide dissipating section for microwave radio energy;

Another object of the present invention is to provide an improved high power dummy load for waveguide transmission systems;

Another object of the present invention is to provide an improved power absorbing material for waveguide at tenuators;

Another object of the present invention is to provide microwave radio power absorbing material for waveguide attenuators which absorbs negligible amounts of moisture;

Another object of the present invention is to provide a dielectric power absorbing material which provides a high attenuation of microwave radio energy;

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawings, forming a part of the specification, wherein:

FIG. 1 is a perspective view of a preferred embodiment of a waveguide in accordance with the present invention;

FIG. 2 is a fragmentary perspective view of the waveguide of FIG. 1 with one section of the waveguide removed;

FIG. 3 is a sectional View of the waveguide taken along line 33 of FIG. 2; and

FIG. 4 is a chart illustrating the method of preparing the improved dielectric power absorbing material.

FIG. 1 illustrates a waveguide 1 for microwave radio energy having an energy transmitting central duct defined by broad walls 2 and narrow walls 3. The integral fins 4 of the preferred embodiment are provided to dissipate the heat generated in the power absorbing material 6 in the waveguide side walls.

FIG. 2 illustrates a preferred embodiment of a slot in the broad wall 2 for the power absorbing material 6.

Slot 5 consists of elongated outer portions 7 extending a substantial distance along the broad wall 2 adjacent the wall edges and a shorter center portion 8.

In order to facilitate the retention of the power absorbing material in the slots 5, a series of vertical ridges 9 are preferably provided in spaced relation in the slot 5 as best illustrated in FIG. 3. The dielectric power absorbing material 6 is contained in the slots 5.

The preferred material 6 comprises a fused mixture of iron powder and a silica binder such as powdered glass or porcelain. A suitable powdered glass or porcelain is marketed under the trade name Copper Enamel. A preferred mixture ratio for the powdered iron and the silica binder is about 1.8 parts by weight of the powdered glass to one part of powdered iron. Pure iron powder is preferably used which has been reduced by hydrogen from its oxide form.

The iron powder is first mixed with the powdered binder and the mixture is ball milled in order to completely coat the iron powder with the silica binder. A milling period of 8 hours provides such a coating of the iron powder. This coating of the iron powder with the glass provides an extremely high attenuation rate in the material. The powder sizes are not critical and mesh sizes of from to 200 mesh have been found to be suitable but other sizes may be used.

After the mixing is completed, water is added to the mixture in sufficient quantities to provide a workable water paste and the paste is applied to the slots 5 in the waveguide side walls. Slots 5 may be provided in any number of the side walls as desired and where a high rate of attenuation is required in a relatively short length of the waveguide slots 5 are provided in each of the waveguide side walls.

After the water paste is applied to slots 5, the paste is baked at a temperature well below the fusing point of the glass but high enough to evaporate the water in a convenient period. A baking temperature of F. is suitable. The dry mixture in the slots is now preferably compressed such as by using an arbor press to level the material at the surface of the walls and to minimize shrinkage during the subsequent firing step. The coated waveguide section is now fired at a temperature high enough to fuse the glass powder such as about 1350 F. to 1400 F. for approximately 5 minutes or until the material turns an orange-red color. This firing step melts the glass or porcelain so that it forms a fused mass with the iron powder. The heat is now removed and the waveguides are allowed to cool at room temperature.

A waveguide 1 as illustrated in FIG. 1 with the absorbing material applied in one or more side walls as described above may be used as a through section in a waveguide transmission line to provide a predetermined degree of attenuation or the section may be used as a high power dummy load by shorting one end of the waveguide section.

It has been found that the absorbing material described above adheres tightly to the slot in the walls of the waveguide so that an efficient heat transfer is provided through the waveguide side walls to the atmosphere around the fins 4 or alternatively through fluid cooling jackets or coils. In addition, the fused nature of the material prevents the absorption of Water and the attendant danger resulting from the generation of steam when high power is transmitted to or through the waveguide section. Waveguides having absorbing material as described also have a high and a constant attenuation rate even after being subjected to high temperatures and rapid temperature cycling.

As various changes may be made in the form, construction and arrangement of the parts herein Without departing from the spirit and scope of the invention and without sacrificing'any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim: 7 p

1. A Waveguide dissipating section comprising the combination of a metal tube, a slot formed on an interior wall of said tube, and a dielectric power absorbing means in said slot comprising a fused mass of iron and glass formed from iron powder and powdered glass having a melting temperature of about 1300 to 1500 F.

2. The waveguide as claimed in claim 1 which comprises about two parts by weight of powdered glass to one part of iron powder.

3. The method of forming a dielectric power absorbing means in a slotted waveguide wall which comprises mixing about two parts by weight of a powdered glass with one part by weight of iron powder, ball milling said mixture to coat the iron particles with glass, forming a workable water paste of the mixture and applying the wet paste to the waveguide wall slot, baking the paste to dry it, and heating the dry paste above the melting temperature of the glass at about 1300 to 1450 F. to form a fused mass from the dry paste on said waveguide Wall.

4. The method of forming a power absorbing means in a slot in an inner wall of hollow metal waveguide which comprises mixing two parts by weight of a powdered glass with one part by Weight of iron powder, ball milling said mixture to coat the iron particles with the glass,

forming a workable water paste of the mixture and ap plying it to the said waveguide wall, baking said mixture to evaporate the water, compressing the dried mixture, heating the compressed mixture at the melting temperature of the powdered glass at about 1300 to 1450 F. to form a fused mass from the mixture on said waveguide wall, and thereafter cooling the waveguide to room temperature.

References Cited by the Examiner UNITED STATES PATENTS 1,714,683 5/1929 Lowry 252-625 1,868,327 7/1932 Kramer Q. 252-625 2,450,532 10/1948 Tognola 106-46 2,676,307 4/1954 Anderson 333-22 2,804,598 8/1957 Pano 333-22 2,855,630 10/1958 Veley 264-112 X 2,857,338 10/1958 ROlfs et a1. 333-22 2,875,418 2/1959 Rolfs 333-22 2,908,875 10/1959 Blatt 333-22 2,923,689 2/1960 Saltzman 252-624 2,977,672 4/1961 Telfer 29-1555 2,986,804 6/1961 Greenman et al. 29-1555 3,123,470 3/1964 Denison.

HERMAN KARL SAALBACH, Primary Examiner.

RUDOLPH V. ROLINEC, Examiner. 

1. A WAVEGUIDE DISSIPATING SECTION COMPRISING THE COMBINATION OF A METAL TUBE, A SLOT FORMED ON AN INTERIOR WALL OF SAID TUBE, AND A DIELECTRIC POWER ABSORBING MEANS IN SAID SLOT COMPRISING A FUSED MASS OF IRON AND GLASS FORMED FROM IRON POWDER AND POWDERED GLASS HAVING A MELTING TEMPERATURE OF ABOUT 1300 TO 1500* F.
 3. THE METHOD OF FORMING A DIELECTRIC POWER ABSORBING MEANS IN A SLOTTED WAVEGUIDE WALL WHICH COMPRISES MIXING ABOUT TWO PARTS BY WEIGHT OF A POWDERED GLASS WITH ONE PART BY WEIGHT OF IRON POWDER, BALL MILLING SAID MIXTURE TO COAT THE IRON PARTICLES WITH GLASS, FORMING A WORKABLE WATER PASTE OF THE MIXTURE AND APPLYING THE WET PASTE TO THE WAVEGUIDE WALL SLOT, BAKING THE PASTE TO DRY IT, AND HEATING THE DRY PASTE ABOVE THE MELTING TEMPERATURE OF THE GLASS AT ABOUT 1300* TO 1450* F. TO FORM A FUSED MASS FROM THE DRY PASTE ON SAID WAVEGUIDE WALL. 